Introduction: The Reasons for Antipsychotic Discontinuation Interview (RAD-I) was developed to assess patients’ perceptions of reasons for discontinuing or continuing an antipsychotic. The current study examined reliability and validity of domain scores representing three factors contributing to these treatment decisions: treatment benefits, adverse events, and distal reasons other than direct effects of the medication.Methods: Data were collected from patients with schizophrenia or schizoaffective disorder and their treating clinicians. For approximately 25% of patients, a second rater completed the RAD-I for assessment of inter-rater reliability.Results: All patients (n = 121; 81 discontinuation, 40 continuation) reported at least one reason for discontinuation or continuation (mean = 2.8 reasons for discontinuation; 3.4 for continuation). Inter-rater reliability was supported (kappas = 0.63–1.0). Validity of the discontinuation domain scores was supported by associations with symptom measures (the Positive and Negative Syndrome Scale for Schizophrenia, the Clinical Global Impression – Schizophrenia Scale; r = 0.30 to 0.51; all P < 0.01), patients’ primary reasons for discontinuation, and adverse events. However, the continuation domain scores were not significantly associated with these other indicators.Discussion: Results support the reliability, convergent validity, and known-groups validity of the RAD-I for assessing patients’ reasons for antipsychotic discontinuation. Further research is needed to examine validity of the RAD-I continuation section.